1. Field of the Invention
The present invention relates generally to a method and an apparatus for manufacturing printed light guide plates, particularly printed light guide plates used for liquid crystal display devices.
2. Prior Art
Since liquid crystal material in a liquid crystal display panel does not itself emit light, a light source module, such as a back light module, must be used with the liquid crystal display panel in order to provide the needed illumination. The back light module provides the liquid crystal display panel with a homogeneous surface light source having sufficient luminance. The light source module comprises a light guide plate, which is a key element for generating the homogeneous surface light source.
FIG. 1 illustrates a typical light guide plate 1. The light guide plate 1 comprises a transparent slab 11, and a plurality of scattering dots 12. The transparent slab 11 has a first surface 111 for emitting homogeneous surface light, a second surface 112 opposite to the first surface 111, and a side surface 113 for receiving incident light from a light source such as a fluorescent light tube. The scattering dots 12 are disposed on the second surface 112, in order to destroy the total internal reflection of the incident light. This enables homogeneous light to emit through the first surface 111.
There are in general two manufacturing processes for manufacturing the light guide plate 1; that is, a printing process and a non-printing process. A typical printing process comprises the steps of: injection molding the transparent slab 11; printing the plurality of scattering dots 12 on the second surface 112 of the transparent slab 11, the scattering dots 12 comprising materials such as SiO2 or TiO2 having high light scattering characteristics; and curing the transparent slab 11 in order to fix the scattering dots 12 on the second surface 112.
However, the transparent slab 11 may absorb moisture from the air before the printing process actually commences, and this may reduce the quality of the printed scattering dots 12. In addition, the printed transparent slab 11 may absorb water and organic solution from the printing ink. As a result, the transparent slab 11 may deform during the curing process. Therefore, a new manufacturing method and supporting apparatus that overcome these problems is needed.